system("cd $sd") doesn't behave the way you think it does. It starts the cd command, which immediately exits again. The current directory of the parent process (your Perl script) is not changed.

To change the directory, see chdir. Also see File::Find, if you haven't already.

find2perl makes this easy. It takes the same arguments as the find command and produces a script for you. It comes with perl on unix, linux and Windows.

Running the command

find2perl /some/directory -name '*.gz' -exec gunzip {} \;
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produces

#! /usr/bin/perl -w
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
        if 0; #$running_under_some_shell

use strict;
use File::Find ();

# Set the variable $File::Find::dont_use_nlink if you're using AFS,
# since AFS cheats.

# for the convenience of &wanted calls, including -eval statements:
use vars qw/*name *dir *prune/;
*name   = *File::Find::name;
*dir    = *File::Find::dir;
*prune  = *File::Find::prune;

sub wanted;
sub doexec ($@);


use Cwd ();
my $cwd = Cwd::cwd();


# Traverse desired filesystems
File::Find::find({wanted => \&wanted}, '/some/directory');
exit;


sub wanted {
    /^.*\.gz\z/s &&
    doexec(0, 'gunzip','{}');
}


sub doexec ($@) {
    my $ok = shift;
    my @command = @_; # copy so we don't try to s/// aliases to consta
+nts
    for my $word (@command)
        { $word =~ s#{}#$name#g }
    if ($ok) {
        my $old = select(STDOUT);
        $| = 1;
        print "@command";
        select($old);
        return 0 unless <STDIN> =~ /^y/;
    }
    chdir $cwd; #sigh
    system @command;
    chdir $File::Find::dir;
    return !$?;
}
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Is this limited to *NIX? FWIW, you can merge your system calls into one:

for my $sd (@dirs) {
   system(qq{cd "$sd" && gunzip *.gz});
}
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to change the current directory do as the following example:

Now cwd holds the full path to the working directory. Hope this helps...

find top_dir/ -type f -name '*.gz' | xargs gunzip
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system("cd $sd && gunzip *.gz");
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